Crystal-wire filament for incandescent electric lamps and the method of winding it



May 1, 1928. 6 1,668,016

M. HAUSCHILD ET AL CRYSTAL WIRE FILAMENT FOR INCANDESCENT ELECTRIC LAMPS AND THE METHOD OF WINDING IT Filed Feb. 23. 1926 i m HAUBOHILD, OI DBESDEN, AND WALTER BERGER, OI 3mm, GIB- m, ASSIGNOBB TO RIDE GLUHLAIPBN-GW m 1 vi r Patented May 1, 1928.

UNITED STATES v. l,668,0l6 PATENT OFFICE.

HAI'TU'HG, OI DBESDEN, SAXOITY, (13mm.

CRYSTAL-WIRE IILAHEN'I' FOB INCANDEBCEM BLIGIBIC nam s All)! men 01' WINDING 1'1.

Application fled rem-nary 28, 1826, Serial Io. 80,188, and in. Germany llovember ll, am.

If the light-eflect of an incandescent electric lamp is to be intensified it is essential for its length of filament to be crowded into as small aspace as possible, a process which is specially difiicult to perform where filaments of an length have to be thus arranged. Suc a crowded arrangement of the incandescent part of a lamp brings about a far greater intensity of light in the case of an incandescent gas lamp, than it does in a vacuum bulb, inasmuch as the loss of light occasioned by radiation and carrying off of heat is in that case reduced to a minimum. The thus increased intensity of light also renders a lamp suitable for projection and Searchlight purposes, for which, hitherto, the electric arc lamp with all its well-known disadvantages had to be employed whenever great intensity of light was required, because, up to date, it was not possible to roduce a wire that could resist very great eats wihout distorting or sagging.

Careful experiments have now established the fact, that a crystal wire containing tungsten for instance, is excellently suited for withstanding great heats, provided this is subjected to special treatment. Furthermore the fact was established, that such wire could easily be coaxed into the required form. But other similar metals may also be employed with similar favourable results.

According to the invention here claimed, ready-formed long or single crystal wire or filament, containing tungsten for instance, is wound on a core of comparatively big sectional out, which, however, is not circular in appearance but shows alternatively sharp and quite flat bends or perfectly straight stretches and is twisted in such a manner, that these straight or only slightly bent stretches of the separate screw-like twists of the core are arranged at a varying angle to each other round the. axis of the core, i. e., round the incandescent body of the lamp, so that. when seen as a wholein the direction of the axis, they present a sectional view as completely as possible covered with filament wires.

This, according to the invention claimed,

is obtained in the two following ways:

1. The wire, brought to white heat, is bent, i. e., wound round a core such as shown in Fig.. of the drawing which resembles alo w-p1tched worm, but the inclination of pitch of which, for example, always presents a triangular sectional view, i. e., three straight stretches, f, f and f" and three acute angles between these in such a manner, that every complete turn of the wire describes the form of a triangle, the third or end corner of which is, however. not closed, but is se arated from the beginning of the triange by a distance equal to the height of pitch of the worm-like core, whilst each turn of the wire, in addition, has an angle of twist of at least 5, measured from the axis of the latter.

Owing to this peculiar method of winding the white-hot crystal wire on the core, as described, the finished filament, seen in line with its axis, presents a web of wires, more or less crowded together, according to the number of threads of the said screwor worm-like core and covering almost the entire cross section. If the wires are arranged so that at least a few of the straight or only slightly bent stretches thereof pass through the axis of the finished filament it will be found, that even the central portion of the said web, when seen in the direction of said axis, is not free from filament wire, (as shown in Fig. 3 corresponding to Fig. 3) in other words, that there is no gap so that the whole of the incandescent part of a lamp is a completely glowing surface. Now the uniformity of arrangement of this extraordinary, intensively glowing surface can be rendered more or less perfect, according to the number of turns performed in the screw-like winding of the filament and according to the number of the more or less straight stretches of wire crowded together.

The crystal wire, ready-formed for the purpose and wound up at white heat, retains the form imparted to it by the process of bending and winding on to this core,

even after the latter is removed. The ob servation of certain details in the process-of winding, can, however. impart a certain deformity to the resultant filament. Thus. for instance, the speed at which the wire is wound or its temperature or tension, or all these considerations together, can bring about a certain, more or less distinct tension in the wire and this tension, after remoral of the core, causes the wire to assume a certain form, differing from that of the core upon which it was wound. A careful observation of these details during the wirewinding process-details that have been determined b appropriate tests and experiments-wil? result in the production of a quite definite form of filament as soon as the core is removed. The said details, here enumerated, are all calculated to overcome the difiiculties as well in the shaping of an exactly suitable core as well as those encountered in the process of winding the wire and in removing the ore after the winding is completed.

Owing to its peculiar shape and production from ready-formed long crystal wire, as well as the peculiar method of winding it, the filament product will not alter even after frequent burning in the lamp. Concussions and vibrations will not affect it and, if desired, it need not even be supported in its centre or at most but once.

2. The second method of winding is also performed with crystal wire, ready formed for the purpose but kept at a very low temperature, i. e., not in aglowing condition and only just sufiiciently heated to prevent it from being brittle and just easily bendable. In this case the wire is wound s iral- 1y over a c0re.-a section of which atter is almost circular in appearance but has atleast one, more or less segment flattened gart about it,-or two cores, at a suitable istance from, and firmly connected to each' other are used.

The two cores, here referred to, are illustrated by a and b of Figs. 1 and 2 of the accompanying drawing, the first of which shows this method of winding in a section perpendicular to the core, whilst the second is a side view of the same.

Figs. 3 and 4 show the finished filament wound in this manner after removal of the cores a and b, the respective views corresponding to Figs. 1 and 2.

Fig. 3 is aside view of a finished filament before being mounted in a lamp.

Fig. 5 shows a bulb fitted with a filament made according to this invention.

Fig. 6 1s a perspective view of a core witha few windings of the filament thereon.

Experiments have shown, that the wire a, wound on the double core a and b as seen in Figs. 1 and 2 and kept at a low temperature during the winding process. acquires a sharp twist at the bends, i. e., where the wire has come in contact with the cores and furthermore receives an inner tension, which latter, on removal from the cores, causes the said wire to further screw-like twist itself round the axis of the parallel cores a and b in such a manner, that, when looked at in line with this axis it will have the shape or form of filament depicted in Fig. 3, by way of example. The same wire, seen perpendicularly to this axis will have the appearance as shown in Fig. 4.

The number of cross wires as seen in Fig.

3 can be increased at number of complete winding, each straight stretch of wire of one turn, compared with the corresponding straight stretch of another turn showin a different an 1e round the axis of the finished filament. 1% can be arranged, for example, that the two straight stretches formin the sides of a bend or angle are given a twist, so that the angle of difference in the direction of these same two stretches amounts to but 5. Where very long filament wires are to be crowded together, the available space will be covered by a correspondingly large number of turns of the wire, 50 that the said space, as seen in Fig. 3 is crossed and recrossed with straight wires, leaving no free space between them.

It is possible to even cross the space (I (Fig. 3) with such straight lengths of wire, if at least one of these be drawn through the axis of the complete filament. I

The space d of Fig. 3 can, however, also be left free for the insertion of a rod e by way of support for the wire a. This rod e, consisting of an insulating material such as magnesia or thorium oxide, etc., will attain a white heat under the'influence of the high temperature developed by the filament and will thus also add its share to the brightness of light.

Experiments have proved, that it is possible in this manner to produce a filament from single crystal wire, which at 1000 watts and volts occupies the space of a cylinder of but 14 mm. length and 10 mm. diameter and which burns constantly in a bulb without any central support being required for it. Even repeated switching on and off of the current or strong vibrations have been unable to alter the good quality of this filament, which presents a perfectly uniform incandescent surface in a direction crossing the axis of the filament. V

The incandescent electric filament enclosed in a vacuum bulb as seen in Fig. 5 is made in accordance with the invention here claimed. The said filament c is seen to be joined to the leads 9 and at f and f without requiring any furt er support. The end h of the filament wire is arranged over the middle of the incandescent surface and seen in line with the axis of the filament.

According to the temperature and tension of the wire 0, the speed at which it is wound on the core, as well as the shape of the core itself, it is ible to make the angle of turn round t 0 core more or less acute and thus to obtain a eater or lesser number of sinew-lilre stretc es of wire with any dowill, according to the turns performed in sired twist, so that the total area as seen in Fi 3 can be covered therewith, always provi ing the wireto be long enough for that pur a v Tmurns round the core, which in Fi 3 appear as points of a star, have a suitab e inner tension and the sinew-like stretches of wire are corres ndingl countertaxed by this tension, so t at the f orm, automatically imgarted to the filament wire by this process an in this manner, remains perfectly reliable and constant without the core and do not vary in any ways under even the influence of the greatest heat or the severest vibrations. 7

Having now particularly described and ascertained the nature of our invention and the manner in which it is made and applied,

we declare that what we claim and desire to secure by Letters Patent of" the United States is .1. Method of producing filaments for elec: tric incandescent lamps from wires of metals having a very high melting temperature by bending ready-formed long crystal wire over a mandrel other than circular, by permitting the spiral thus wound to relax, after removal of the mandrel, into the shape according to the inner mechanical tension of the bent wire and by then inserting the filament in theform thus assumed into an incandescent lamp.

2. Met 0d of producing filaments for electric incandescent lamps from wires of metals having a very high melting temperature by bendi ready-formed long crystal wire over a man rel, other than circular, permitting the s iral thus wound to relax, after remova of the mandrel, into the sha according to the inner mechanical tenslon of the bent wire and by then inserting the filament in the form thus assumed into an incandescent lam 3. Met 0d of producing filaments for electric incandescent lamps from'wires of metals having a very high melting temperature by bendin read '-formed long crystal wire over a man rel ot er than circular, consisting of two wires arranged at a distance from one another, by permitting the spiral thus wound to relax, after removal of the mandrel, into the shape according to the inner mechanical tension of the bent wire and by then insertin the filament in the form thus assume into an incandescent lamp.

In testimony whereof we aflix our signatures.

MAX HAUSCHILD. WALTER BERGER. 

